Use a tank of freon (3M Fluorinert), ala Cray in the old days

Interesting info:
Each cable between the modules was a twisted-pair, cut to a specific length in order to guarantee the signals arrived at precisely the right time and minimize electrical reflection. Each signal produced by the ECL circuitry was a differential pair, so the signals were balanced. This tended to make the demand on the power supply more constant and reduce switching noise. The load on the power supply was so evenly balanced that Cray boasted that the power supply was unregulated. To the power supply, the entire computer system looked like a simple resistor.
 
The high-performance ECL circuitry generated considerable heat, and Cray's designers spent as much effort on the design of the refrigeration system as they did on the rest of the mechanical design. In this case, each circuit board was paired with a second, placed back to back with a sheet of copper between them. The copper sheet conducted heat to the edges of the cage, where liquid Freon running in stainless steel pipes drew it away to the cooling unit below the machine. The first Cray-1 was delayed six months due to problems in the cooling system; lubricant that is normally mixed with the Freon to keep the compressor running would leak through the seals and eventually coat the boards with oil until they shorted out. New welding techniques had to be used to properly seal the tubing. The only patents issued for the Cray-1 computer concerned the cooling system design.

Back to Back 8x8 16chip Jalleys in freon...